| Evaluation of XPath Expressions. | *|
|---|---|
| context | ** If a request is made to evaluate the expression in the absence * of a context item, an empty document node will be used for the context. * For the purposes of evaluating XPath expressions, a DocumentFragment * is treated like a Document node. * | *
| variables | ** If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver} * set with {@link #setXPathVariableResolver(XPathVariableResolver resolver)}. * An {@link XPathExpressionException} is raised if the variable resolver is undefined or * the resolver returns {@code null} for the variable. * The value of a variable must be immutable through the course of any single evaluation. * | *
| functions | ** If the expression contains a function reference, the function will be found through the {@link XPathFunctionResolver} * set with {@link #setXPathFunctionResolver(XPathFunctionResolver resolver)}. * An {@link XPathExpressionException} is raised if the function resolver is undefined or * the function resolver returns {@code null} for the function. * | *
| QNames | ** QNames in the expression are resolved against the XPath namespace context * set with {@link #setNamespaceContext(NamespaceContext nsContext)}. * | *
| result | ** This result of evaluating an expression is converted to an instance of the desired return type. * Valid return types are defined in {@link XPathConstants}. * Conversion to the return type follows XPath conversion rules. * | *
An XPath object is not thread-safe and not reentrant. * In other words, it is the application's responsibility to make * sure that one {@link XPath} object is not used from * more than one thread at any given time, and while the {@code evaluate} * method is invoked, applications may not recursively call * the {@code evaluate} method. * * @author Norman Walsh * @author Jeff Suttor * @see XML Path Language (XPath) Version 1.0 * @since 1.5 */ public interface XPath { /** * Reset this {@code XPath} to its original configuration. * *
{@code XPath} is reset to the same state as when it was created with * {@link XPathFactory#newXPath()}. * {@code reset()} is designed to allow the reuse of existing {@code XPath}s * thus saving resources associated with the creation of new {@code XPath}s. * *
The reset {@code XPath} is not guaranteed to have the same * {@link XPathFunctionResolver}, {@link XPathVariableResolver} * or {@link NamespaceContext} {@code Object}s, e.g. {@link Object#equals(Object obj)}. * It is guaranteed to have a functionally equal {@code XPathFunctionResolver}, * {@code XPathVariableResolver} and {@code NamespaceContext}. */ public void reset(); /** * Establish a variable resolver. * *
A {@code NullPointerException} is thrown if {@code resolver} is {@code null}. * * @param resolver Variable resolver. * * @throws NullPointerException If {@code resolver} is {@code null}. */ public void setXPathVariableResolver(XPathVariableResolver resolver); /** * Return the current variable resolver. * *
{@code null} is returned in no variable resolver is in effect. * * @return Current variable resolver. */ public XPathVariableResolver getXPathVariableResolver(); /** * Establish a function resolver. * *
A {@code NullPointerException} is thrown if {@code resolver} is {@code null}. * * @param resolver XPath function resolver. * * @throws NullPointerException If {@code resolver} is {@code null}. */ public void setXPathFunctionResolver(XPathFunctionResolver resolver); /** * Return the current function resolver. *
* {@code null} is returned in no function resolver is in effect. * * @return Current function resolver. */ public XPathFunctionResolver getXPathFunctionResolver(); /** * Establish a namespace context. * *
A {@code NullPointerException} is thrown if {@code nsContext} is {@code null}. * * @param nsContext Namespace context to use. * * @throws NullPointerException If {@code nsContext} is {@code null}. */ public void setNamespaceContext(NamespaceContext nsContext); /** * Return the current namespace context. * *
{@code null} is returned in no namespace context is in effect. * * @return Current Namespace context. */ public NamespaceContext getNamespaceContext(); /** * Compile an XPath expression for later evaluation. * *
If {@code expression} contains any {@link XPathFunction}s, * they must be available via the {@link XPathFunctionResolver}. * An {@link XPathExpressionException} will be thrown if the * {@code XPathFunction} * cannot be resovled with the {@code XPathFunctionResolver}. * *
If {@code expression} contains any variables, the * {@link XPathVariableResolver} in effect * at compile time will be used to resolve them. * * @param expression The XPath expression. * * @return Compiled XPath expression. * @throws XPathExpressionException If {@code expression} cannot be compiled. * @throws NullPointerException If {@code expression} is {@code null}. */ public XPathExpression compile(String expression) throws XPathExpressionException; /** * Evaluate an {@code XPath} expression in the specified context and * return the result as the specified type. * *
* See Evaluation of XPath Expressions * for context item evaluation, variable, function and {@code QName} resolution * and return type conversion. *
* The parameter {@code item} represents the context the XPath expression * will be operated on. The type of the context is implementation-dependent. * If the value is {@code null}, the operation must have no dependency on * the context, otherwise an XPathExpressionException will be thrown. * * @implNote * The type of the context is usually {@link org.w3c.dom.Node}. * * @param expression The XPath expression. * @param item The context the XPath expression will be evaluated in. * @param returnType The result type expected to be returned by the XPath expression. * * @return The result of evaluating an XPath expression as an {@code Object} of {@code returnType}. * * @throws XPathExpressionException If {@code expression} cannot be evaluated. * @throws IllegalArgumentException If {@code returnType} is not one of the types defined in {@link XPathConstants} ( * {@link XPathConstants#NUMBER NUMBER}, * {@link XPathConstants#STRING STRING}, * {@link XPathConstants#BOOLEAN BOOLEAN}, * {@link XPathConstants#NODE NODE} or * {@link XPathConstants#NODESET NODESET}). * @throws NullPointerException If {@code expression or returnType} is {@code null}. */ public Object evaluate(String expression, Object item, QName returnType) throws XPathExpressionException; /** * Evaluate an XPath expression in the specified context and return the result as a {@code String}. * *
This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a {@code returnType} of * {@link XPathConstants#STRING}. * *
See Evaluation of XPath Expressions for context item evaluation, * variable, function and QName resolution and return type conversion. * *
* The parameter {@code item} represents the context the XPath expression * will be operated on. The type of the context is implementation-dependent. * If the value is {@code null}, the operation must have no dependency on * the context, otherwise an XPathExpressionException will be thrown. * * @implNote * The type of the context is usually {@link org.w3c.dom.Node}. * * @param expression The XPath expression. * @param item The context the XPath expression will be evaluated in. * * @return The result of evaluating an XPath expression as a {@code String}. * * @throws XPathExpressionException If {@code expression} cannot be evaluated. * @throws NullPointerException If {@code expression} is {@code null}. */ public String evaluate(String expression, Object item) throws XPathExpressionException; /** * Evaluate an XPath expression in the context of the specified {@code InputSource} * and return the result as the specified type. * *
This method builds a data model for the {@link InputSource} and calls * {@link #evaluate(String expression, Object item, QName returnType)} on the resulting document object. * *
See Evaluation of XPath Expressions for context item evaluation, * variable, function and QName resolution and return type conversion. * * @param expression The XPath expression. * @param source The input source of the document to evaluate over. * @param returnType The desired return type. * * @return The {@code Object} that encapsulates the result of evaluating the expression. * * @throws XPathExpressionException If expression cannot be evaluated. * @throws IllegalArgumentException If {@code returnType} is not one of the types defined in {@link XPathConstants}. * @throws NullPointerException If {@code expression, source or returnType} is {@code null}. */ public Object evaluate( String expression, InputSource source, QName returnType) throws XPathExpressionException; /** * Evaluate an XPath expression in the context of the specified {@code InputSource} * and return the result as a {@code String}. * *
This method calls {@link #evaluate(String expression, InputSource source, QName returnType)} with a * {@code returnType} of {@link XPathConstants#STRING}. * *
See Evaluation of XPath Expressions for context item evaluation, * variable, function and QName resolution and return type conversion. * * @param expression The XPath expression. * @param source The {@code InputSource} of the document to evaluate over. * * @return The {@code String} that is the result of evaluating the expression and * converting the result to a {@code String}. * * @throws XPathExpressionException If expression cannot be evaluated. * @throws NullPointerException If {@code expression or source} is {@code null}. */ public String evaluate(String expression, InputSource source) throws XPathExpressionException; /** * Evaluate an XPath expression in the specified context and return * the result with the type specified through the {@code class type} * *
* The parameter {@code item} represents the context the XPath expression * will be operated on. The type of the context is implementation-dependent. * If the value is {@code null}, the operation must have no dependency on * the context, otherwise an XPathExpressionException will be thrown. * * @implNote * The type of the context is usually {@link org.w3c.dom.Node}. * * @implSpec * The default implementation in the XPath API is equivalent to: *
{@code
* (T)evaluate(expression, item,
* XPathEvaluationResult.XPathResultType.getQNameType(type));
* }
*
* Since the {@code evaluate} method does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying
* XPathEvaluationResult as the type will result in IllegalArgumentException.
* Any implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override
* this method.
*
* @param {@code
* evaluateExpression(expression, item, XPathEvaluationResult.class);
* }
* * The parameter {@code item} represents the context the XPath expression * will be operated on. The type of the context is implementation-dependent. * If the value is {@code null}, the operation must have no dependency on * the context, otherwise an XPathExpressionException will be thrown. * * @implNote * The type of the context is usually {@link org.w3c.dom.Node}. * * @implSpec * The default implementation in the XPath API is equivalent to: *
{@code
* evaluateExpression(expression, item, XPathEvaluationResult.class);
* }
*
* Since the {@code evaluate} method does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY}
* type, the default implementation of this method will always throw an
* IllegalArgumentException. Any implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore
* override this method.
*
* @param expression The XPath expression.
* @param item The context the XPath expression will be evaluated in.
*
* @return The result of evaluating the expression.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If the implementation of this method
* does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.
* @throws NullPointerException If {@code expression} is {@code null}.
*
* @since 9
*/
default XPathEvaluationResult evaluateExpression(String expression, Object item)
throws XPathExpressionException
{
return evaluateExpression(expression, item, XPathEvaluationResult.class);
}
/**
* Evaluate an XPath expression in the context of the specified {@code source}
* and return the result as specified.
* * This method builds a data model for the {@link InputSource} and calls * {@link #evaluateExpression(String expression, Object item, Class type)} * on the resulting document object. The data model is usually * {@link org.w3c.dom.Document} * * @implSpec * The default implementation in the XPath API is equivalent to: *
{@code
(T)evaluate(expression, source,
XPathEvaluationResult.XPathResultType.getQNameType(type));
* }
*
* Since the {@code evaluate} method does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying
* XPathEvaluationResult as the type will result in IllegalArgumentException.
* Any implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override
* this method.
*
* @param {@code
* evaluateExpression(expression, item, XPathEvaluationResult.class);
* }
*
* @implSpec
* The default implementation in the XPath API is equivalent to:
* {@code
* evaluateExpression(expression, source, XPathEvaluationResult.class);
* }
*
* Since the {@code evaluate} method does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY}
* type, the default implementation of this method will always throw an
* IllegalArgumentException. Any implementation supporting the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore
* override this method.
*
* @param expression The XPath expression.
* @param source The input source of the document to evaluate over.
*
* @return The result of evaluating the expression.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If the implementation of this method
* does not support the
* {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.
* @throws NullPointerException If {@code expression or source} is {@code null}.
*
* @since 9
*/
default XPathEvaluationResult evaluateExpression(String expression, InputSource source)
throws XPathExpressionException
{
return evaluateExpression(expression, source, XPathEvaluationResult.class);
}
}